Cancer of unknown primary during pregnancy: an exceptionally rare coexistence.

BACKGROUND Cancer in pregnancy is a rare disease with breast cancer, cervical cancer, melanoma and Hodgkin's disease to be the most commonly diagnosed malignancies during gestation. Cancer of unknown primary (CUP) is a well-recognized clinical disorder where the primary site can not be identified after a standard diagnostic approach. CUP in pregnancy has rarely been described. MATERIALS AND METHODS We searched MEDLINE and contacted cancer Centers in Europe, United States and Australia where patients with CUP or pregnant patients with cancer were diagnosed and treated. RESULTS Since 1976 we identified 18 pregnant women with CUP in a median gestational age of 34 weeks. Most of these patients were diagnosed with poorly-differentiated histology, had poor response to systemic treatment and a median maternal survival of 8 months. Seventy-two percent of mothers have died, while 80% of the newborns were alive and healthy. Almost one fourth of placentas examined showed metastatic disease. CONCLUSION CUP during pregnancy is a very rare coexistence, usually has an aggressive disease with poor response to chemotherapy and a dismal prognosis. Both obstetricians and oncologists should be aware of this rare condition.